Luminescent materials in matrices are known in the art. US2006055316 for instance describes color electroluminescent displays comprising a sub-pixel structure and method for making the same. The sub-pixel structure has an electroluminescent phosphor, which emits blue light, and a photo luminescent phosphor, which emits at least one other color as a result of absorption of the blue light. US2006055316 also describes such photo luminescent phosphor materials. For instance, this document describes a method for making a photo luminescent phosphor material, the method comprising mixing a pigment powder and a matrix material to provide a uniform dispersion of the pigment powder in the matrix material, wherein the pigment material comprises a solid solution of organic photo luminescent molecules, the matrix material being chemically and physically compatible with the pigment powder such that the photo luminescent efficiency of the organic photo luminescent molecules are substantially maintained.